1) Field of the Invention
The present invention relates to an oil pan provided in an oil circulatory system such as a mechanical apparatus or a power apparatus, and more particularly, to an oil pan with a built-in filtering element.
2) Description of the Related Art
Conventionally, in an oil circulatory system such as the mechanical apparatus and the power apparatus, there is a known oil pan for storing circulation oil therein is added to a lower portion of an apparatus which uses oil. For example, the oil pan is added to a lower portion of an engine or a transmission of a vehicle such as an automobile, oil in the oil pan is pumped up using an oil pump, the oil is supplied to the engine or transmission, and oil used by the engine or transmission is collected into the oil pan and is circulated.
In such an oil circulatory system, a filtering element such as an oil filter (simply “filter”, hereinafter) which filters circulation oil is usually provided upstream from the oil pump.
For example, Japanese Patent Application Laid-open No. H8-42319 (prior art 1, hereinafter) discloses a structure in which such a filter is disposed in the oil pan. According to this conventional structure, a closing plug for closing a drain hole through which oil remaining in the oil pan is discharged at the time of maintenance is devised, and a filter is held in the oil pan using the closing plug. Further, Japanese Patent Application Laid-open No. 2002-364325 (prior art 2, hereinafter) discloses a structure in which a filter is disposed in the oil pan. According to this conventional structure, a baffle plate disposed in the oil pan comprises main plate and sub-plate made of synthetic resin, a passenger-shaped strainer chamber is formed between both the plates, and a mesh plate sandwiched between the main plate and sub-plate is disposed in the strainer chamber.
Since the filter is embedded in the oil pan, the oil circulatory system can be simplified.
According to the structure of the prior art 1, however, the filter is held in the oil in a state where the filter largely projects from a tip end of the closing plug, and when vibration or the like is applied to the oil pan and the oil laterally swings with respect to the filter, the filter largely receives influence of lateral swing of the oil, and since the filter is supported only at its one end and supporting rigidity is insufficient and thus, the filter is prone to receive influence of vibration input.
Further, there is a problem that the structure of the closing plug is complicated and the assembling operability of the filter is poor.
According to the structure of the prior art 2, the filter is held by the baffle plate having a large area mounted on an upper portion of the oil pan. Therefore, especially when vibration or the like is applied to the oil pan, the filter is prone to receive influence of the vibration, and if the input vibration is large, the filter may be damaged in some cases. When the position of an oil pump is changed, the shape or the like of the baffle plate (especially shape of the main plate) must be changed, and there is a problem that the design of the baffle plate must largely be changed.
Further, there is a problem that the oil pan has large volume as a part which is added to a lower portion of an apparatus which uses oil such as an engine and a transmission, and since the conventional oil pan is made of metal, its weight is increased.